Fuel injection valve for internal combustion engines

ABSTRACT

In a fuel injection valve, in order to ensure that minimal or no fuel pressure is exerted in a closing direction on the valve needle when the latter is in an open position, the supply channel leading from the downstream side of the valve seat to the nozzle openings circumvents the valve needle and the latter, in said open position, hermetically engages with its base face a stationary frontal plate held in the valve.

United States Patent 1 1 3,593,925

[72] Inventors Konrad Eckert; 1 References Cited Heinz Links, both of Stuttgart, Germany UNITED STATES PATENTS [21} AppLNo. 10,459 2,647,015 7/1953 Berlyn 239/533 1 1 Filed -1 .19 0 2,647,016 7/1953 Berlyn .1 239/533 45 Patented J ly 20,1971 2.592.111 4/1952 Bischot' 239/533 I Asslgnee g z zf lgfir igf FOREIGN PATENTS [32] Priority Feta y 686,943 1/1940 Germany 1. 239 533 cermally 835,672 4/1952 Germany 239/533 [3) P19 0734]] 835,819 4/1952 Germany 1. 239/533 Primary Examiner Lloyd L. King Att0rney-Edwin E. Greigg ABSTRACT:I f 1" 1' 1 d 1 m1 54 FUEL INJECTION VALVE FOR INTERNAL er oensure a minimal or no fuel pressure is exerted in a closing direction on the valve needle when the latter is in an open position, the

supply channel leading from the downstream side of the valve 239/533 seat to the nozzle openings circumvents the valve needle and B05!) 1/30 the latter, in said open position, hermetically engages with its 239/533 base face a stationary frontal plate held in the valve.

COMBUSTION ENGINES 7 Claims, 3 Drawing Figs.

FUEL INJECTION VALVE FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to a fuel injection valve for internal combustion engines, Said valve is of the type that includes a valve needle which opens in the direction of fuel flow and which is provided at its terminal portion with a conical valve head and an adjoining cylindrical guide member. During opening motion, the latter projects into a chamber which is defined by the cylindrical guide member, by the valve body accommodating said guide member, and by a frontal plate disposed immediately downstream of the valve body and adjacent the cylindrical guide member.

In a known fuel injection valve of the aforenoted type (disclosed for example in German Pat. No. 835,819), there are provided, in the cylindrical guide member, bores forming part of the pressure channel extending between the valve seat and the injection opening. These bores carry fuel towards the injection opening and converge in the base face of the cylindrical guide member. The common mouth of these bores is disposed opposite a bore which is provided in the adjacent frontal plate and which also serves as part of the pressure channel. For starting the injection, the valve needle is unseated and, as a result, the fuel flows through the aforenoted bores to the nozzle openings. Hereby care should be taken that the frontal face of the cylindrical guide member tightly and accurately engages the frontal plate to ensure that, as far as possible, no faces of the valve needle are exposed to the fuel pressure which would impart a closing force on the valve needle. In practice, however, it is impossible to machine the cooperating faces of the cylindrical guide member and the frontal' plate to ensure a perfect overall contact. Consequently, some fuel will be forced therebetween, the pressure of which, due to a certain throttle effect of the bore in the frontal plate, is higher than the pressure prevailing downstream of the frontal plate and immediately upstream of the nozzle openings.

OBJECT AND SUMMAR Y OF THE INVENTION It is an object of the invention to provide an improved fuel injection valve ,of the aforenoted type from which the aforementioned disadvantages of known fuel injection valves are eliminated.

Briefly stated, according to the invention, the pressure channel extending between the valve seat and the nozzle openings circumvents the cylindrical guide portion and, through a bore which preferably has a throttling effect, is connected with the chamber into which the cylindrical guide portion projects.

According to an embodiment of the invention, the said bore merges into said chamber opposite the frontal face of the cylindrical guide portion.

According to another embodiment of the invention, the aforenoted bore merges into the aforenoted chamber radially with respect to the cylindrical guide member. In the open position of the valve needle, an annular part of the base face of the cylindrical guide member hermetically engages the frontal plate. By virtue of the preferably relatively narrow annular face portion, the specific pressure may be relatively small for ensuring a sufficient seal between the base face of the cylindrical guide member and the frontal plate. Consequently, when the valve needle is in its open position, no hydraulic forces urge the latter in a closing direction.

The invention will be better understood, as well as further objects and advantages will become more apparent, from the ensuing detailed specification of two exemplary embodiments I taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an axial sectional view of a first embodiment of the invention;

FIG. 2 is an axial sectional view of a second embodiment of the invention; and

FIG. 3 is an axial sectional view of a modified structure of the second embodiment. I

DESCRIPTION OF THE EMBODIMENTS In the different embodiments depicted in the figures, elements of identical function and structure are given identical reference numerals, while elements of identical function but of more or less different structure are differentiated by prime signs.

Turning now to the figures, in a valve body I, I there is disposed a valve needle 2 which is adapted to open in the flow direction of the fuel and which is provided with a conical valve head 3. The downstream terminus of the valve needle 2 is formed of guide member 4, 4', 4" which is reciprocable with a snug fit in a bore 5 of the valve body I, l'. The bore 5 narrows into a conical portion fi constituting a valve seat and is then adjoined by a bore 7 into which the fuel is admitted by means of a fuel injection pump (not shown). The bore 7 accommodates the shaft of the valve needle 2. A chamber 8 disposed between the valve seat 6 and the cylindrical guide member 4, 4', 4" and defined by the valve body 1, 1' and the valve needle 2, is connected with a pressure chamber 10, 10' of the fuel injection valve by means of a supply channel 9, 9'. From the chamber I0, 10' there extend the injection ports or nozzle openings 11. The supply channel 9, 9' extends partially in the valve body 1, l and partially in a frontal plate 12, l2, 12" which covers the bore 5. From the supply channel 9, 9' there extends a bore 13, 13' to a space 14, 14', 14" into which projects the front part of the cylindrical guide member 4, 4, 4" during opening of the valve. The last-named chamber is definedby the frontal plate l2, 12', 12'', the wall of the bore 5 and the base face 15, 15, 15" of the cylindrical guide member 4, 4', 4".

When, by virtue of fuel delivery by the fuel injection pump, the valve needle 2 is displaced downstream in the opening direction, the cylindrical guide member 4, 4', 4" displaces the fuel quantity immediately downstream of its base face I5, l5, 15" through bore 13, 13' into the supply channel 9, 9 and therefrom into the pressure chamber 10, 10. The said fuel dis placement is terminated at the moment when the base face l5, 15, 15'' engages the frontal plate 12, l2, l2". By virtue of such engagement, very small or no hydraulic forces affect the valve needle in the closing direction. While the valve needle 2 is in its open position, fuel injection continues through injection ports 11 which are in communication with the bore 7. As soon as the fuel supply by the fuel injection pump is terminated, the fuel injection valve is closed by means of a closing spring (not shown) operatively connected to the valve needle 2. Upon this occurrence, fuel flows through the bore l3, 13 into the space 14,14, 14''.

Turning now to FIG. I, in the embodiment shown therein the bore 13 is formed as a throttle bore and merges, opposite the base face 15 of the cylindrical guide member 4, into the space 14. The valve body 1, as well as the frontal plate 12, is held within the nozzle body 17. The base face 15 and the immediately adjacent face of the frontal plate 12 are planar so that when these two faces are in contact, only that portion of the base face 15 is exposed to a pressure in the closing direction of the valve needle which covers the throttle bore 13. The result is a relatively very small force in that direction. Even in case the last-mentioned faces are separated from one another, although the static hydraulic pressure prevailing between the two separated faces would be as large as in the pressure chamber I0, with the smallest displacement of the valve needle 2 in the closing direction, the pressure would be reduced by virtue of the throttle bore I3. This feature constitutes a substantial improvement over the structures known in the prior art.

Turning now to FIGS. 2 and 3, in the embodiment shown therein, the bore 13' (which is not necessarily a throttle) merges into the space l4, l4" radially with respect to the cylindrical guide member 4', 4". Further, the chamber in order to maintain the harmful space" at a possibly small value, is arranged directly in the frontal plate 12, 12". The latter is secured to the valve body 1 by means of a screw cap 18. In this embodiment, after the opening of the valve, an annular part 19, 19" of the base face l5, engages hermetically the frontal plate l2, 12'. The said annular part is relatively narrow in order to maintain a relatively high specific pressure at the sealing face. As soon as the annular face l9, 19 is in engagement with the frontal plate l2, 12', the fuel can no longer affect the base face l5, 15" in the closing direction of the valve needle.

in FIG. 2, the annular sealing face 19 is planar and is delimited by an arcuate, cavitylike central portion of the base face 15'. Accordingly, the cooperating adjacent face of the frontal plate 12' is also planar.

In FIG. 3, the annular sealing face 19" is formed as a conical portion of base face [5". In the center of the frontal plate 12" there is provided a conical depression 20 complemcntal with said sealing face 19''.

That which we claim is:

I. In a fuel injection valve of the known type that includes (A) a valve body incorporating an internal valve seat having a downstream and an upstream side, (B) a valve needle reciprocably disposed in said valve body and adapted to open in the direction of fuel flow, said valve needle including a valve head cooperating with said valve seat, said valve needle further including a cylindrical guide member, (C) a frontal plate stationary with respect to said valve body and disposed adjacent said cylindrical guide member, (D) a space into which said cylindrical guide member projects during the opening motion of said valve needle, said space delimited by said cylindrical guide member, said valve body and said frontal plate, and (E) nozzle openings for injecting said fuel, the improvement comprising:

A. a supply channel connecting the downstream side of said valve seat with said nozzle openings, said channel extending spaced from said cylindrical guide member, and B. a bore maintaining communication between said channel and said space.

2. An improvement as defined in claim 1, wherein said bore has a throttling effect.

3. An improvement as defined in claim 2, wherein said cylindrical guide member has a base face, said bore opens into said space opposite said base face.

4. An improvement as defined in claim 1, wherein said bore opens into said space radially with respect to said cylindrical guide member.

5. An improvement as defined in claim 1, wherein said cylindrical guide member has a base face which includes an annular edge portion hermetically engaging said frontal plate when said valve needle is in its open position.

6. An improvement as defined in claim 5, wherein said annular edge portion is delimited by a cavitylike portion of said base face.

7. An improvement as defined in claim 5, wherein said annular edge portion is formed as a conical surface, said frontal plate is provided with a conical depression complemental with said conical surface to receive the latter when said valve needle is in its open position. 

1. In a fuel injection valve of the known type that includes (A) a valve body incorporating an internal valve seat having a downstream and an upstream side, (B) a valve needle reciprocably disposed in said valve body and adapted to open in the direction of fuel flow, said valve needle including a valve head cooperating with said valve seat, said valve needle further including a cylindrical guide member, (C) a frontal plate stationary with respect to said valve body and disposed adjacent said cylindrical guide member, (D) a space into which said cylindrical guide member projects during the opening motion of said valve needle, said space delimited by said cylindrical guide member, said valve body and said frontal plate, and (E) nozzle openings for injecting said fuel, the improvement comprising: A. a supply channel connecting the downstream side of said valve seat with said nozzle openings, said channel extending spaced from said cylindrical guide member, and B. a bore maintaining communication between said channel and said space.
 2. An improvement as defined in claim 1, wherein said bore has a throttling effect.
 3. An improvement as defined in claim 2, wherein said cylindrical guide member has a base face, said bore opens into said space opposite said base face.
 4. An improvement as defined in claim 1, wherein said bore opens into said space radially with respect to said cylindrical guide member.
 5. An improvement as defined in claim 1, wherein said cylindrical guide member has a base face which includes an annular edge portion hermetically engaging said frontal plate when said valve needle is in its open position.
 6. An improvement as defined in claim 5, wherein said anNular edge portion is delimited by a cavitylike portion of said base face.
 7. An improvement as defined in claim 5, wherein said annular edge portion is formed as a conical surface, said frontal plate is provided with a conical depression complemental with said conical surface to receive the latter when said valve needle is in its open position. 